Localized milled golf club face

ABSTRACT

A wood-style golf club head includes a strike face and a body that cooperate to define a hollow internal club head volume. The strike face formed from a strike plate having an outer perimeter and a frame surrounding the strike plate. The strike plate is affixed to the frame across the entire outer perimeter. The strike plate and frame define a continuous ball striking surface that has a surface texture characteristic of milling that extends continuously across both the strike plate and the frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This is continuation of U.S. patent application Ser. No. 16/723,026,filed on Dec. 19, 2019, now U.S. Pat. No. 10,857,430, which claimspriority to U.S. Provisional Patent Application No. 62/784,199, filed onDec. 21, 2018, and is a continuation in part of U.S. patent applicationSer. No. 16/438,268, filed on Jun. 11, 2019, now U.S. Pat. No.10,596,423, which is a continuation of U.S. patent application Ser. No.15/847,812, filed on Dec. 19, 2017, now U.S. Pat. No. 10,343,034, whichclaims the benefit of priority from U.S. Provisional Patent ApplicationNo. 62/435,944, filed Dec. 19, 2016, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to a metal wood golf clubhaving a milled ball striking surface and a set of golf clubs havingmilled faces.

BACKGROUND

Conventional metal wood golf club heads include a face and a body thatextends rearward from the face. In some embodiments, the face may have aslightly rounded shape in order to provide a straighter and/or longerflight path for a golf ball, even when the ball is struck away from thecenter of the face. This rounded shape may be defined in terms of abulge profile (curvature from a toe end to a heel end) and a rollprofile (curvature from the crown edge to the sole edge).

Typical metal wood golf club heads may be formed by coining and/ormachining a strike plate to have a pre-determined bulge and rollcurvature, welding the strike plate within an opening provided within aforward frame, grinding away any weld bead that is outwardly exposedfollowing the welding process, and then applying a uniform, brushedsurface finish across the frame and strike plate. Such a process,however, can lead to rather large tolerances in the final product due tovariability in the coining, welding, grinding, and finishing processes.As such, there is a need in the art to create a golf club with a faceprofile that can achieve much tighter bulge/roll tolerances to reducethe variability across multiple club heads of the same design. Inaddition, there is a need in low lofted club heads to reduce spinimparted on a golf ball to assist in increasing the carry distance andimproving flight path of the golf ball.

Aspects of the invention will become apparent by consideration of thedetailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a golf club head.

FIG. 2 is a schematic partially exploded perspective view of the golfclub head of FIG. 1.

FIG. 3 is a schematic assembly view of an alternate embodiment of a golfclub.

FIG. 4 is a schematic diagram of a method of forming a golf club head.

FIG. 5 is a schematic diagram of a method of forming a golf club head.

FIG. 6 is a schematic diagram of a method of forming a golf club head.

FIG. 7A is a schematic front side view of a golf club head having alinear vertical milling pattern.

FIG. 7B is a schematic front side view of a golf club head having alinear horizontal milling pattern.

FIG. 7C a schematic rear view of a back surface of a strike face havinga concentric milling pattern extending radially outward from a center.

FIG. 7D is a schematic front view of a strike face having a circularcenter portion with a linear horizontal milling pattern and a peripheralportion with a milling pattern extending radially outward from thecenter portion.

FIG. 7E is a schematic front view of a strike face having a circularcenter portion with a milling pattern extending radially outward from acenter and a peripheral portion with a linear horizontal millingpattern.

FIG. 7F is a schematic front view of a strike face having a circularcenter portion with a milling pattern extending radially outward from acenter and a peripheral portion with a milling pattern havingoverlapping and intersecting linear milling marks.

FIG. 7G is a schematic front view of a strike face having a circularcenter portion with a milling pattern extending radially outward from acenter and a peripheral portion with a milling pattern havingoverlapping and intersecting curvilinear milling marks.

FIG. 7H is a schematic front view of a strike face having a circularcenter portion with a concentric milling pattern extending radiallyoutward from a center and a peripheral portion with a concentric millingpattern extending radially outward from the center portion.

FIG. 7I is a schematic front view of a strike face having a curvedpolygonal center portion with a linear horizontal milling pattern and aperipheral portion with a plurality of zones, each having a differentlyoriented linear milling pattern.

FIG. 7J is a schematic front view of a strike face having a curvedpolygonal center portion with a concentric milling pattern extendingradially inward from an outer periphery and a peripheral portion with aplurality of zones, each having a differently oriented linear millingpattern.

FIG. 7K is a schematic front view of a strike face having a curvedpolygonal center portion with a linear horizontal milling pattern and aperipheral portion with a plurality of zones, each having a differentlyoriented linear milling pattern.

FIG. 8 is a graph that schematically illustrates the computation of thesurface parameter W_(Void).

FIG. 9 is a graph that schematically illustrates the computation of thesurface parameter W_(VDCL).

FIG. 10 is a schematic perspective view of a golf club head illustratinga face-centric coordinate system located at a geometric face center.

FIG. 11 is a graphical representation of the bulge variation between anexemplary golf club head and a normal club head.

FIG. 12 is a graphical representation of the CT variation between anexemplary golf club head and a normal club head.

DETAILED DESCRIPTION

The present embodiments discussed below are generally directed to a golfclub head, methods of making a golf club head, and/or coordinated setsof golf club heads that have milled surface textures across a forwardball striking surface for the purpose of affecting the spin imparted toa golf ball that is impacted by the club head.

Milling a golf club face has been shown to provide a more controlledand/or controllable surface profile, contour, and texture as comparedwith other golf club finishing techniques. When properly executed, ithas been found that a milled surface texture may impart a greater amountof contact friction during the impact with a golf ball than otherfinishing techniques such as brushing. Unfortunately, milling is highlyvariable, and existing measures of surface roughness (e.g., averageroughness (R_(A))) do not properly explain differences between variousmilling patterns. As such, the present disclosure is further directed tomilled ball striking surfaces that are characterized by newly developedsurface parameters, which closely correlate to the amount of spinimparted to a golf ball by a low lofted club, such as a driver (i.e.,where spin reductions in a low-lofted club may be indicative ofincreased contact friction at impact). Using these techniques, thepresently disclosed milled faces have found a reduction in imparted spindespite an approximately equal, or slightly decreased average roughness(R_(A)). This manner of characterizing a milled golf club face mayfurther be employed to create faces that suit different designobjectives (high backspin, low backspin, customized side-spin profiles(e.g., to augment the roll and bulge profile of a driver), zonal millingpatterns to affect off-center impacts, varying spin profiles as afunction of loft, etc.

“A,” “an,” “the,” “at least one,” and “one or more” are usedinterchangeably to indicate that at least one of the item is present; aplurality of such items may be present unless the context clearlyindicates otherwise. All numerical values of parameters (e.g., ofquantities or conditions) in this specification, including the appendedclaims, are to be understood as being modified in all instances by theterm “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; about or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in the artwith this ordinary meaning, then “about” as used herein indicates atleast variations that may arise from ordinary methods of measuring andusing such parameters. In addition, disclosure of ranges includesdisclosure of all values and further divided ranges within the entirerange. Each value within a range and the endpoints of a range are herebyall disclosed as separate embodiment. The terms “comprises,”“comprising,” “including,” and “having,” are inclusive and thereforespecify the presence of stated items, but do not preclude the presenceof other items. As used in this specification, the term “or” includesany and all combinations of one or more of the listed items. When theterms first, second, third, etc. are used to differentiate various itemsfrom each other, these designations are merely for convenience and donot limit the items.

The terms “loft” or “loft angle” of a golf club, as described herein,refers to the angle formed between the club face and the shaft, asmeasured by any suitable loft and lie machine. The geometric center ofthe face, or “face center” is defined in terms of custom and conventionfor identifying the geometric center of the face. As is well understood,the face center is a location that is equidistant between the heel edgeof the face and the toe edge of the face, and equidistant between thetop edge of the face and the bottom edge of the face.

The terms “first,” “second,” “third,” “fourth,” and the like in thedescription and in the claims, if any, are used for distinguishingbetween similar elements and not necessarily for describing a particularsequential or chronological order. It is to be understood that the termsso used are interchangeable under appropriate circumstances such thatthe embodiments described herein are, for example, capable of operationin sequences other than those illustrated or otherwise described herein.Furthermore, the terms “include,” and “have,” and any variationsthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, system, article, device, or apparatus that comprises alist of elements is not necessarily limited to those elements, but mayinclude other elements not expressly listed or inherent to such process,method, system, article, device, or apparatus.

The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,”“under,” and the like in the description and in the claims, if any, areused for descriptive purposes with general reference to a golf club heldat address on a horizontal ground plane and at predefined loft and lieangles, though are not necessarily intended to describe permanentrelative positions. It is to be understood that the terms so used areinterchangeable under appropriate circumstances such that theembodiments of the apparatus, methods, and/or articles of manufacturedescribed herein are, for example, capable of operation in otherorientations than those illustrated or otherwise described herein.

The terms “couple,” “coupled,” “couples,” “coupling,” and the likeshould be broadly understood and refer to connecting two or moreelements, mechanically or otherwise. Coupling (whether mechanical orotherwise) may be for any length of time, e.g., permanent orsemi-permanent or only for an instant.

Other features and aspects will become apparent by consideration of thefollowing detailed description and accompanying drawings. Before anyembodiments of the disclosure are explained in detail, it should beunderstood that the disclosure is not limited in its application to thedetails or construction and the arrangement of components as set forthin the following description or as illustrated in the drawings. Thedisclosure is capable of supporting other embodiments and of beingpracticed or of being carried out in various ways. It should beunderstood that the description of specific embodiments is not intendedto limit the disclosure from covering all modifications, equivalents andalternatives falling within the spirit and scope of the disclosure.Also, it is to be understood that the phraseology and terminology usedherein is for the purpose of description and should not be regarded aslimiting.

Referring to the drawings, wherein like reference numerals are used toidentify like or identical components in the various views, FIG. 1schematically illustrates a perspective view of a wood-style golf clubhead 10 that includes a strike face 12 and a body 14 that cooperate todefine a hollow internal club head volume 16 (shown in FIG. 2). Asshown, the golf club head 10 further includes a toe portion 20, a heelportion 22, a rear portion 24, a crown 26, and a sole 28. While thepresent disclosure is generally made with respect to a wood-style clubhead, such as a driver, fairway wood, or hybrid iron, it should beunderstood that aspects of this disclosure, such as controlling facetexture to affect contact friction and spin, may be equally applicableto iron-type golf clubs.

As generally illustrated in FIGS. 1-2, in some embodiments, the strikeface 12 may include a strike plate 30 and a frame 32 that cooperate todefine a continuous ball striking surface 34 (i.e., the portion of theclub head 10 that is intended to directly impact a golf ball). In anembodiment, the strike plate 30 and frame 32 may be integrally formedfrom a singular piece of material. In some variations of this design,the frame 32 may sweep rearward away from the ball striking surface 34to form a “cup face” portion of the club head.

In another embodiment, instead of being integrally formed, the strikeplate 30 may generally be affixed within an opening 36 provided in theframe 32. For example, in some embodiments, the frame 32 may include alip 38 or recessed shelf that extends around at least a portion of theperimeter of the opening 36. When assembled, the strike plate 30 maynest within the opening 36 such that a rear surface of the strike plate30 abuts the lip 38 and such that the forward surface of the strikeplate 30 is about flush with the forward surface of the frame 32. Oncepositioned within the opening 36, the strike plate 30 may then beaffixed to the frame 32 around the entire perimeter/seam through anintegral attachment technique such as welding.

In an embodiment where the strike plate 30 is formed separate from theframe 32, the strike plate 30 may undergo a coining process prior tobeing affixed within the opening 36. This coining process may impart abulge and/or roll curvature to the ball striking surface 34 to provide amargin of correction for off-center impacts through a dynamic responsegenerally referred to as a “gear effect.” The bulge radius is the radiusmeasured across the strike plate 30 from the toe portion 20 to the heelportion 30. Similarly, the roll radius is the radius of the strike plate30, from the crown 26 to the sole 30.

During the coining process, a large force is applied to the strike plate30 that plastically deforms the material into having the predeterminedcurvature (characterized by a bulge radius of curvature and a rollradius of curvature). In many embodiments, the bulge radius and the rollradius can be the same. In other embodiments, the bulge radius and theroll radius can be different. In the illustrated embodiment, both thebulge and roll have a radius of 12 inches (about 304.8 mm). In otherembodiments, the bulge can have any radius of curvature. For example, insome embodiments, the bulge can have a radius of 4 in, 5 in, 6 in, 7 in,8 in, 9 in, 10 in, 11 in, 12 in, 13 in, 14 in, 15 in, 16 in, 17 in, 18in, 19 in, 20 in, 21 in, 22 in, 23 in, 24 in, 25 in, 26 in, 27 in, or 28in (about 100 mm to about 720 mm). In the same or other embodiments, theroll can have any radius of curvature. For example, in some embodiments,the roll can have a radius of 4 in, 5 in, 6 in, 7 in, 8 in, 9 in, 10 in,11 in, 12 in, 13 in, 14 in, 15 in, 16 in, 17 in, 18 in, 19 in, 20 in, 21in, 22 in, 23 in, 24 in, 25 in, 26 in, 27 in, or 28 in (about 100 mm toabout 720 mm).

Referring to FIG. 3, the golf club head 600 can comprise a front body602 and a rear body 604, wherein the front body 602 and rear body 604are separately formed. The strike plate 630 and frame 632 can beintegrally formed to create a “cup face” type front body 602 (may alsobe referred to as simply “cup face 602”). The strike plate 630 and frame632 are integrally formed such that the strike plate 630 and frame 632cooperate to define a ball striking surface 634. The cup face extendsrearward (away from the striking surface 634) to form a portion of thecrown 626 and the sole 628. By forming the entire striking surface 634with the front body 602 allows an entire back surface 635 of thestriking surface 634 to be milled and machined, not just a back surfaceof the strike plate 630. Further, separately forming the entire strikingsurface 634 with the front body 602 allows the back surface 635 toidentically match the milling and machining of the striking surface 634.Milling and/or machining the back surface 635 of the striking surface634, allows the manufacturer to adjust at least one of: a strikingsurface thickness, the bulge radius of the striking surface 634, or theroll radius of the striking surface 634. Matching the inner and outermachining profiles of the striking surface 634 and the back surface 635of the striking surface 634 improves the consistency of thecharacteristic time of the club head 600, as well as the consistency ofthe face thickness, bulge, and roll of the club head 600.

In some cases, referring to FIG. 2, wherein the strike plate 30 isformed separately from the body 14 of the club head 10, the strike plate30 has to be individually machined for each golf club, to account forsmall inconsistent bulge and roll dimensions following the creation ofthe strike plate 30 and the surrounding frame 32. Referring back to FIG.3, by forming the strike plate 630 and surrounding frame 632 integrally,as part of a front body 602, the machining process becomes quicker andmore precise, since the contour of the striking surface 634 can bechanged on two surfaces rather than one. Further, the consistency of thegolf club head produced by the process increases, since themanufacturing tolerances can be improved, without increasing costs.Furthermore, the integral formation of the strike plate 630 andsurrounding frame 632 eliminates the process of welding the strike plate630 to the surrounding frame 632, thus further improving the consistencyof the resulting face thickness, bulge, roll, and CT of the front body602.

The frame 32 and/or strike plate 30 may be formed from the same materialor different materials, so long as they both are constructed withsufficient strength to withstand repeated impact stresses that occurwhen the club head 10 strikes a golf ball. Examples of suitablematerials for the frame 32 and/or strike plate 30 include stainlesssteel or steel alloys (e.g., C300, C350, Ni(Nickel)-Co(Cobalt)-Cr(Chromium)-Steel Alloy, 565 Steel, AISI type 304or AISI type 630 stainless steel), a titanium alloy (e.g., a Ti-6-4,Ti-3-8-6-4-4, Ti-10-2-3, Ti 15-3-3-3, Ti 15-5-3, Ti185, Ti 6-6-2, Ti-7s,Ti-92, or Ti-8-1-1 Titanium alloy), an amorphous metal alloy, aluminumalloys, or one or more high strength composite materials comprising, forexample, plastic polymers and co-polymers, carbon fibers, fiberglassfibers or metal fibers.

The club head body 14 can be formed from the same material or adifferent material than the frame 32 and/or strike plate 30. In someembodiments, the material of the body 14, together with the design ofthe body structure, may provide a controlled dynamic impact response,which may affect launch angle, spin and ball speed. In some embodiments,the body 14 may be formed from stainless steel, titanium, aluminum,steel alloys, titanium alloys, carbon fiber composites, molded filled orunfilled engineering plastics/polymers, or combination thereof.

FIG. 4 illustrates a first method 100 for forming the golf club headassembly 10. This first method 100 includes a first step 102 of formingthe strike plate 30 and the club head body 14. The strike plate 30and/or club head body 14 may be formed using processes such asmachining, casting, stamping, injection molding (metal and/or polymer),direct laser sintering, powder metal forming processes, or otherappropriate process known to those skilled in the art.

Once formed into a general shape, the strike plate blank may then becoined in step 104. As noted above, coining is form of precisionstamping, wherein the strike plate 30 is subjected to a high forcecausing it to plastically deform. The coining process is used to createthe bulge and roll radius described above.

The strike plate 30 may then be milled or machined in step 106 toprovide a precision contour and surface texture. The machining processuses a rotary cutter to remove material from the strike plate 30 and isgenerally performed using a CNC system to control the process.

Once machined, the strike plate 30 may then be welded into the opening36 of the frame 32 in step 108. The strike plate 30 is aligned with theopening 36 of the frame 32 and abuts the lip 38. The strike plate 30 issecured to the frame 32 by welding along the perimeter of the opening 36forming the golf club head 10. In some embodiments, the welding step mayutilize a pulse plasma or laser welding process.

Following the welding process in step 108 the weld line and anyprotruding weld bead may be removed through a grinding process in step110. The grinding process involves a rotating abrasive wheel used toremove material along the weld line. The grinding process can alsoensure that the bulge and roll radius of the frame 32 matches the bulgeand roll radius of the strike plate 30 created during coining andmachining steps 104, 106. A golf club head assembly 10 formed from themethod 100 illustrated in FIG. 4 will include a strike face 12 that hasat least two different surface finishes (i.e., the original and/orground finish of the frame 32 and the machined/milled finish of thestrike plate 30).

FIG. 5 schematically illustrates a second method 200 for forming a golfclub head 10. The method 200 illustrated in FIG. 4 is similar in manyrespects to the first method 100 illustrated in FIG. 4, except themachining/milling of step 106 is performed after the strike plate 30 iswelded to the frame 32 in step 108. In doing so, the grinding process ofstep 110 may be optionally removed, and the surface texture of thestrike plate 30 may be optionally extended across the frame 32 in acontinuous manner.

The second method 200 generally begins by forming the strike plate 30and golf club head body 14 in step 202, such as by machining, casting,stamping, injection molding (metal and/or polymer), direct lasersintering, powder metal forming processes, or other appropriate processknown to those skilled in the art. The strike plate 30 may then becoined in step 204, as described above in step 104 of FIG. 4.

The coined strike plate 30 may then be welded into the opening 36provided in the frame 32 in step 206. Any remaining weld bead/line maythen be optionally removed via a grinding process 208 (illustrated inphantom to indicate that this process is not a strictly required step).And finally, the entire ball striking surface 34 may be machined/milledin step 210. In some embodiments, this machining step 210 may beoperative to remove any weld bead that was not removed via optional step208.

By machining/milling across the entire ball striking surface 34, thismanufacturing method 200 may create a surface texture with no or littleregard for the specific location of the weld line/perimeter of thestrike plate 30. For example, the surface texture may be uniform andcontinuous across both the strike plate 30 and frame 32, maycontinuously vary as a function of a distance from face center, or takeany other pattern as may be found desirable. Most importantly, thesemilling patterns need not be constrained by the size and location of thestrike plate perimeter.

Milling or machining the entire strike face 12, such as through thesecond method 200 of FIG. 5, provides an additional benefit of furthertightening/reducing the profile/curvature tolerances for the bulge androll radius (i.e., to provide a more precise curvature). Having thetextured surface across the entire strike face 12 while maintaining alower tolerance for the bulge and roll radius can create a higherperforming club head assembly 10 that provides greater distance, spincontrol, and forgiveness.

Further, in some embodiments the strike plate 30 and frame 32 can beintegrally formed into a face cup front body 502. In some cases, whenthe strikeplate 30 is welded into the frame 32 (in method 100 or 200),the CT of the striking surface can be inconsistent (i.e., “hot spots”are formed on the strike face, wherein the strike face is slightlythinner than other parts of the strike face) since the welding formsslight undulations on the rear surface of the strike plate. Although theaforementioned methods 100, 200 machine, mill, and/or grind the frontsurface of the striking surface (tightening the bulge and roll of thestrike face), these methods 100, 200 do not account for the CTinconsistency of the strike face created by slight deformations andundulations of the rear surface.

Referring to FIG. 11, the bulge radii of 30 golf club heads (referred toas “Normal Club” in FIG. 11) formed by a method does not machine or millthe strike face were compared to the bulge radii of 30 golf club heads(referred to as “Exemplary Club”) formed by method 100 or method 200. Itcan be seen in FIG. 11, that the bulge radii of the Normal Club variedacross 30 club heads by 30 mm. In comparison, the bulge radii of theExemplary Club varied across 30 club heads by only 10 mm (a 66.67%improvement in the bulge radii consistency. As aforementioned, methods100, 200 improve the overall consistency and manufactured precision ofthe face strike face profile (bulge, roll, face thickness) of a golfclub head.

However, as previously discussed, although methods 100, 200 improve thestrike face profile, they often time create CT variances across multiplegolf club heads. This leads to inconsistent strike faces, across aproduct line, which is undesirable. Referring to FIG. 12, theCharacteristic Times of 30 golf club heads (referred to as “Normal Club”in FIG. 12) formed by a method does not machine or mill the strike facewere compared to the Characteristic Times of 30 golf club heads(referred to as “Exemplary Club” in FIG. 12) formed by method 100 ormethod 200. It can be seen that, the CT of the Normal Club Varied across30 club heads by 10 μs. In comparison, the Ct of the Exemplary Clubvaried across 390 club heads by 25 μs. Therefore, even though methods100 and 200 improve the strike face profile, the CT consistency of themanufactured golf club head is very inconsistent.

FIG. 6 schematically illustrates a third method 500 for forming a golfcub head 600. The method 500 includes a first step 502 of forming thefront body 602 and read body 604. The front body 502 and rear body 602may be formed using processes such as machining, casting, stamping,injection molding (metal and/or polymer), direct laser sintering, powdermetal forming processes, or other appropriate process known to thoseskilled in the art.

The striking surface 634 of the front body 602 may then be milled ormachined in step 504 to provide a precision contour and surface texture.The machining process uses a rotary cutter to remove material from thestriking surface 634 and is generally performed using a CNC system tocontrol the process.

The back surface 635 of the striking surface 634 may then be milled ormachined in step 506 to provide a further precision contour and/orsurface texture, over the contour and surface texture, provided by theaforementioned methods 100, 200. The surface texture of the back surface635, in some embodiments is, identical to the milling and/or machiningon the striking surface 634. The machining process uses a rotary cutterto remove material from the strike plate 30 and is generally performedusing a CNC system to control the process.

The front body 602 and rear body 604 can then be connected in step 508to form golf club head 600. The front body 602 and rear body 604 can beconnected through any one or combination of the following: adhesion(epoxy, glue, resin, etc.) a mechanical fixation technique (studs,screws, posts, mechanical interference engagement, etc.), welding,brazing, laser welding, ultrasonic welding or any other suitable methodof connection.

Milling or machining the front 634 and back surfaces 635 of the entirefront body 602, such as through method 500, provides an additionalbenefit of further tightening/reducing the profile/curvature tolerancesfor the bulge and roll radius (i.e., to provide a more precisecurvature), over methods 100 and 200. Having the textured surface acrossthe entire strike face 12 while maintaining a lower tolerance for thebulge and roll radius can create a higher performing club head assemblythat provides greater distance, spin control, and forgiveness.Subsequently, this method 500, improves the consistency of the strikingsurface 634 CT, and therefore creates golf club heads that have similar,and USGA conforming, strike face thickness and CT measurements.

Surface Texture

In a general sense, a milled strike plate 30 has a surface texture thatcan be characterized by one or more directional cutting patterns and asurface texture that is directionally dependent. Typical millingprocesses utilize a rotary cutting tool to remove material from thestrike plate 30. This process can be automated using a ComputerNumerical Control (CNC) system to provide enhanced precision,consistency, and repeatability across multiple club heads. Furthermore,the CNC machining process can ensure that a predominant patterndirection, surface texture, and overall face contour precisely match thepredetermined specifications. This level of enhanced precision isdesirable because it has been found that the predominant patterndirection and surface texture on the strike plate 30 can meaningfullyimpact the spin characteristics on the golf ball after impact.Therefore, given the level of manufacturing control and repeatabilitythat is afforded by CNC milling, it is possible to customize thetextured surface on the strike plate 30 to an individual's swing type,which may result in longer and straighter ball flight patterns.

A typical milling pattern may resemble a plurality of grooves that areconcentrically or linearly cut into the outer surface. These patternsmay more specifically comprise a plurality of primary peaks and primaryvalleys that each extend along a linear or curvilinear path. In someembodiments where milling paths overlap, each primary peak may include aplurality of secondary valleys that are disposed in a regular patternalong at least a portion of the length of the peak, and each primaryvalley may include a plurality of secondary peaks that are disposed in aregular pattern along at least a portion of the length of the valley. Insome embodiments of the present designs, and depending on the directionalong the striking plate surface you measure, the plurality of peaks andvalleys (measured from a mid-plane of the peaks and valleys) can rangefrom −100 μ-in to 100 μ-in (about −2.54 μm to about 2.54 μm), −140 μ-into 140 μ-in (about −3.56 μm to about 3.56 μm), −200 μ-in to 200 μ-in(about −5.08 μm to about 5.08 μm), −500 μ-in to 500 μ-in (about −12.7 μmto about 12.7 μm), −700 μ-in to 700 μ-in (about −17.78 μm to about 17.78μm), −1000 μ-in to 1000 μ-in (about −25.4 μm to about 25.4 μm), −1400μ-in to 1400 μ-in (about −35.56 μm to about 35.56 μm), or more.

While in some embodiments, the surface texture across the ball strikingsurface 34 may be uniform across the entire strike plate 30, in otherembodiments, however, the ball striking surface 34 may have a surfacetexture that functionally varies across the strike face 12. For example,in an embodiment, the surface texture may vary from a center region ofthe strike plate 30 towards the perimeter of the strike plate 30. Insome embodiments, the surface roughness can vary on the strike plate 30from near the toe portion 20 of the club head 10 to near the heelportion 22 of the club head 10. In other embodiments, the surfaceroughness can vary on the strike plate 30 from near the sole 28 of theclub head 10 to near the crown 26 of the club head 10. In still otherembodiments, surface roughness can vary in any combination of theaforementioned examples. In still other embodiments, surface roughnesscan be uniform in certain areas of the strike plate 30, and vary inother areas of the strike plate 30. In an embodiment, the texturedsurface of the strike plate 30 may have a uniform roughness of about 148μ-in (about 3.76 μm). In other embodiments, the textured surface canhave a surface roughness between about 50 μ-in and about 300 μ-in(between about 1.27 μm and about 7.62 μm). In some embodiments, thetextured surface can have a surface roughness between 25-350, 25-50,50-75, 75-100, 75-100, 100-125, 125-150, 150-175, 175-200, 200-225,225-250, 250-275, 275-300, 300-325 μ-in, 25-150, 150-350, 75-250,25-125, 125-225, 225-350, 75-150, 150-225, or 225-300. In otherembodiments, the roughness can be 25, 50, 75, 100, 125, 150, 175, 200,225, 250, 275, 300, 325, or 350 μ-in. In still other embodiments, thesurface roughness can be between about 140 μ-in and about 300 μ-in(between about 3.56 μm and about 7.62 μm).

As generally illustrated in FIGS. 7A-7K, the predominant patterndirection of the textured surface in any particular area may compriseone or more linear, curvilinear, or intersecting patterns to form amilling pattern 250. In some embodiments, these patterns may extendsomewhat uniformly across the entire strike face 12. In otherembodiments, however, these patterns may be zonal, or may vary acrossthe face due to a curvilinear and concentric nature. In someembodiments, the milling pattern 250 may comprise a center portion 252that is surrounded by a peripheral portion 254, such as shown in FIGS.7D-5K. The milling profiles illustrated in FIGS. 7A-7K are examples ofdifferent milling patterns 250 that may be employed to meet differentdesign objectives, as will be discussed below. It should be appreciatedthat additional designs may be developed by combining aspects of eachfigure, and every combination of pattern and shape for the centerportion 252 and pattern and shape of the peripheral portion 254 isregarded as a separate embodiment, even if not illustrated.

As schematically shown in FIG. 7A, in an embodiment, a milling pattern250 may include a plurality of peaks and valleys that are oriented in alinear manner between the crown 26 and the sole 28. FIG. 7B thenillustrates an embodiment where this pattern is turned 90 degrees andextends between the heel portion 22 and toe portion 20. FIGS. 7A and 7Bfurther illustrate a channel 256 that may be disposed around a perimeterof the milling pattern 250 to provide a more pronounced transitionbetween the milling pattern 250 and the remainder of the club 10. Asfurther shown, in some embodiments, an edge portion 258 of the forwardmost surface (i.e. the ball striking surface 34), may not include themilling texture. Such a surface may instead be polished or sandblastedto more readily blend into the body.

FIG. 7FD-7K more clearly illustrate examples of milling patterns 250that have different variations of a center portion 252 and a peripheralportion 254. As shown in FIGS. 7D-7 g, in some embodiments, the centerportion 252 may be round. In other embodiments, such as shown in FIGS.7I-7K, the center portion 252 may have a rounded polygonal design, suchas a rounded triangle or a rounded square (or a rounded pentagon,hexagon, heptagon, octagon, or the like). As further illustrated inFIGS. 7F-7I, the milling pattern 250 within the center portion 252 maycomprise a linear pattern (FIGS. 7D, 7I, and 7K), a concentric pattern,for example, beginning at an outer perimeter of the center portion 252(FIGS. 7H and 7J), or a radial pattern originating from a point, line,or area (FIGS. 7E-7G).

The peripheral portion 254 may comprise one or more zones 260 betweenwhich the milling pattern may change direction/orientation, change type,or begin anew. For example, FIGS. 7K-7M illustrate three peripheraldesigns that include a plurality of zones 260, where a linear pattern isrotated between each zone 260. FIG. 7F illustrates an emanating raypattern (i.e., where the milling lines emanate linearly from a centralpoint or area. FIG. 7G illustrates a linear arrangement across theperipheral portion 254. FIG. 7H illustrates an intersecting lineararrangement (i.e., where a first linear arrangement is cut, and then asecond linear arrangement in a second orientation is cut over top of thefirst linear arrangement). FIG. 7I illustrates intersecting curvilineararrangements (i.e., where the first curvilinear arrangement is cut fromtoe to heel, and the second is cut from heel to toe—note that similararrangements may be made by cutting from crown to sole and sole tocrown, or from various corners). FIG. 7J illustrates a concentricpattern emanating from a central point or area.

In some embodiments, the strike face 12 of the golf club head assembly10 can comprise two or more different surface finishes/textures. Forexample, as described above with respect to FIG. 4, the strike plate 30can be milled or machined, creating a first surface finish prior tobeing welded to the opening 36 of the frame 32. The remaining portion ofthe strike face 12 which was not milled may then have a second surfacefinish, such as a smooth or sand blasted surface finish. Having thedifferent textured surfaces on the strike face 12 can provide the playerwith a visual alignment aid to help position the golf ball at the centerof the strike face 12. In other embodiments, the entire ball strikingsurface 34 (including the frame 32 and strike plate 30) can comprise thetextured surface from the milling or machining process.

While a milled face is beneficial in terms of providing a morecontrolled face curvature, the surface texture and milling patterncreated by the tool can introduce a considerable amount of variabilityin the resulting spin and launch characteristics of an impacted ball.For example, two clubs with milling patterns oriented 90 degrees apartmay produce significantly different ball launch characteristics.Furthermore, even if patterns are oriented similarly, differences in thefeed rate, cutting depth, tool diameter, end profile, and the toolspindle speed used to create the pattern can introduce variations in thesurface texture that affect ball flight.

Through testing, it has been found that traditional measures of surfaceroughness do not appear to properly characterize the effects ofdifferent surface textures and/or milling patterns. For example, Table 1illustrates 4 identical driver designs (i.e., similar volume, massdistribution, structure, and loft), one with a traditional brushedsurface finish across the strike face 12 (i.e, the control club), andthree with different milled surface finishes across the strike face 12.For each club, the average surface roughness (R_(A)) was measured alonga vertical line extending through the geometric center of the face (i.e.from sole 28 to crown 26).

TABLE 1 Imparted backspin for different driver face surface roughnessR_(A) Spin Club (μ · inch) (rpm) Driver - Brushed 147 3005 Driver -Milled 1 144 2683 Driver - Milled 2 221 2840 Driver - Milled 3 284 2817

In this analysis, the first milled face (milled 1) attempted to matchthe average roughness of the brushed surface finish as closely aspossible. Despite the close average roughness, the milled face producedabout 10.7% less spin than the brushed face. This decrease in spin ratewas an unexpected result. Then, milled faces 2 and 3 were constructed toincrease the average roughness, as the prevailing belief was that, asaverage roughness increases, spin imparted by a driver should decrease.Milled faces 2 and 3, however, both resulted in about 5% more spin thanthe lower roughness milled face (milled 1). From this analysis, it wasdetermined that average surface roughness may not be suitable to fullycharacterize the spin-effects caused by the surface texture of a driverface (which is counter to the prevailing understanding).

Following additional investigation, a new manner of characterizing thesurface texture of a strike face has been developed to more effectivelypredict the resulting spin imparted to a golf ball by a strike face.Furthermore, embodiments of the present design utilize this newcharacterization to provide a golf club with a face that is optimized tomeet one or more spin-based design objectives.

Two new surface parameters have been found to more accuratelycharacterize how the surface texture of a golf face may affect the spinof an impacted golf ball. These parameters include: (1) the ratio ofR_(A) to a surface void parameter referred to as W_(Void) (describedbelow); and (2) the value of a surface contact parameter referred to asW_(VDCL) (also described below). To eliminate any ambiguity R_(A),W_(Void), and W_(VDCL) are defined as follows:

R_(A)—As is known in the art, R_(A) represents an arithmetic averagevalue of absolute surface deviations relative to a mean center line. Inpractice, the deviations and mean center line are computed following theapplication of a high-pass filter with a cut-off selected to eliminatesurface waviness. In the present designs, a suitable cut-off wavelengthmay be about 0.03 inches (about 0.762 mm).

W_(Void)—As generally illustrated in FIG. 8, W_(Void) is a parameterthat has been developed to represent the average profile void depth 300relative to a reference surface 302 that is created by applying amorphological closing filter to the actual surface profile 304.Morphologic closing is generally an image processing technique that maybe best analogized as a disc 306 (in 2D) or sphere (in 3D) of apredetermined radius 308 (i.e., radius of curvature) being theoreticallyrolled across the actual surface profile 304. The lower envelope formedby the rolling disc then generates the “closed” reference surface 302.In a two-dimensional context, such as illustrated in FIG. 7, W_(Void)may be calculated by summing the total void area 310 between the closedreference surface 302 the actual surface profile 304 and dividing thataggregated area by the length of the surface (i.e., the length of a meancenter line 312).

W_(VDCL)—As generally illustrated in FIG. 9, W_(VDCL) is a parameterthat has been developed to represent the ratio of the contact length 314(in 2D) or area (in 3D) between the closed reference surface 302 (asdescribed above with respect to W_(Void) and FIG. 7) and the actualsurface profile 304, to the length (in 2D) or area (in 3D) of thesurface itself (i.e., measured along a mean center line 312). For aperfectly flat surface, W_(VDCL) would equal 1.0; for a wavy surface(e.g., where the radius of curvature 308 of the disc/sphere is smallerthan any external radius of curvature of the surface), W_(VDCL) may begreater than 1.0; and, for a surface with a rather fine texture (e.g.,where the radius of curvature 308 of the disc/sphere is greater than anexternal radius of curvature for a portion of the surface), W_(VDCL) maybe less than 1.0.

When computing R_(A), W_(Void), and W_(VDCL), each parameter may becalculated in a number of directionally dependent manners. Morespecifically, the surface profiles illustrated in FIGS. 8 and 9 may bepresumed to have been taken from a 2-D cutting plane through a strikeface 12, similar to the strike face 12 shown in FIG. 1. If this cuttingplane is oriented perpendicular to the dominant milling grooves, allthree surface parameters may differ from measurements where the cuttingplane is oriented parallel to the milling grooves, which may differstill from a 3D computation where any closed reference surface isgenerated by a theoretical sphere.

For the purpose of this disclosure, a face-centric coordinate system400, such as shown in FIG. 10 may be utilized to better explain how theparameters are derived. As shown in FIG. 10, the face-centric coordinatesystem 400 may have an origin that is coincident with the geometric facecenter, X and Y axes 402, 404 that are each tangential to the ballstriking surface 34 at the face center, and a Z-axis 406 that is normalto the ball striking surface at 34 the face center. The X-axis 402 mayfurther be parallel to a ground plane 408 when the club is held ataddress according to prescribed loft and lie angles, and may generallyextend between the heel and the toe. The Y-axis 404 is orthogonal to theX-axis 402, and is generally the projection of a vertical reference line410 onto the ball striking surface 34 when the club is held at address.

When computing the various parameters, each may be computed along a 2Dline (e.g., computed within a single 2D slice taken in the Y-Z plane),averaged across a plurality of 2D lines (e.g., averaged across aplurality of 2D slices taken in adjacent Y-Z planes), or computed in 3Dacross the entire face (i.e., not directionally-dependent).

It is believed that R_(A)/W_(Void) and W_(VDCL) both provide slightlydifferent approximations of the amount of surface area that a golf ballmay directly contact (at a microscopic level) during an impact (i.e.,thus providing a more accurate estimation of the actual contact frictionexperienced between the ball and the face during an impact). Morespecifically, the “closed” reference surface 302 may approximate acompliant object (i.e., a polymeric, compressible golf ball) that is inforcible contact with the surface texture and deforms about the peaks.Based on this assumption, the compliant object (golf ball) nevercontacts certain portions of the voids/valleys; thus, the depth and/orsize of the non-contacted portions is largely irrelevant to theeffective force transfer and contact friction between the ball and thestrike face 12. Despite these voids being largely irrelevant, they cansignificantly affect traditional measures of surface roughness. Underthese assumptions, as R_(A)/W_(Void) and W_(VDCL) increase, contactfriction should also increase, which should then decrease the impartedspin for a low-lofted club such as a driver. As illustrated through thefollowing comparative examples, empirical testing data supports thisunderstanding:

Ratio of R_(A) to W_(Void):

Using a high pass filter for R_(A) of about 0.03 inches (about 0.762mm), and a radius of curvature for W_(Void) of about 0.005 inches (about0.127 mm) to create the reference surface 302, it has been found thatthe ratio of R_(A) to W_(Void) correlates to the amount of spin impartedto an impacted golf ball by a low lofted golf club, such as a driver.More specifically, as R_(A) W_(Void) increases, imparted spin decreases,such as generally illustrated in Table 2. The figures in Table 2 wereall calculated within a Y-Z cutting plane that passed through facecenter for drivers with similar overall geometries, constructions, andmass properties.

TABLE 2 Imparted backspin for driver surface textures having differentvalues of R_(A)/W_(Void) R_(A) W_(Void) Spin Club (μ · inch) (μ · inch)R_(A)/W_(Void) (rpm) Driver - Brushed 147 54 2.7 3005 Driver - Milled 1144 18 8.0 2683 Driver - Milled 2 221 33 6.7 2840 Driver - Milled 3 28436 7.89 2817

As shown in Table 2, while the R_(A) values between the brushed face andthe “Milled 1” face are about equal, the ratio of R_(A)/W_(Void) forthese faces is quite different and more predictive of imparted spin.

W_(VDCL)

Using a radius of curvature for W_(VDCL) of about 0.02 inches (about0.508 mm) to form the reference surface 302, it has been found that thevalue of W_(VDCL) correlates to the amount of spin imparted to animpacted golf ball by a low lofted golf club, such as a driver. Morespecifically, as W_(VDCL) increases, imparted spin decreases, such asgenerally illustrated in Table 3. The figures in Table 3 were allcalculated within a Y-Z cutting plane that passed through face centerfor drivers with similar overall geometries, constructions, and massproperties.

TABLE 3 Imparted backspin for driver surface textures having differentvalues of W_(VDCL) R_(A) Spin Club (μ · inch) W_(VDCL) (rpm) Driver -Brushed 147 22% 3005 Driver - Milled 1 144 29% 2687 Driver - Milled 2221 24% 2840 Driver - Milled 3 284 26% 2817Club Face Designs

While the above-referenced characterizations of surface texture may beutilized to characterize the spin-effects of surface textures formed byvarious techniques (e.g., brushing, milling, sandblasting, etc.),milling may provide the most control of the resulting texture in threedimensions across the face. As such, a golf club head 10 may include amilled ball striking surface 34 that has a surface texture characterizedby a R_(A) to W_(Void) ratio and/or by a W_(VDCL) value that iscustomized to suit a particular design objective. Note that for allexamples described below, any numeric values assume a 0.03 inch (about0.762 mm) high-pass cutoff filter for R_(A), a 0.005 inch (about 0.127mm) radius of curvature for creating the reference surface for W_(Void),and a 0.02 inch (about 0.508 mm) radius of curvature for creating thereference surface for W_(VDCL).

In a first embodiment, a low-lofted club, such as a low-loft driver(i.e., having a loft angle of from about 8 to about 14 degrees, or fromabout 8 to about 12 degrees, or from about 8 to about 10 degrees), maybe specifically designed to have a low backspin tendency by including amilled strike face with surface texture characterized by an R_(A) toW_(Void) ratio, measured in a Y-Z plane through the face center, that isgreater than about 4, or greater than about 5, or greater than about 6,or greater than about 7, or greater than about 8, greater than about 9,or greater than about 10. In some embodiments, the R_(A) to W_(Void)ratio can range from 4 to 12, 4 to 8, 8 to 12, 6 to 10, 4 to 6, 36 to 8,8 to 10, or 10 to 12. For example, the R_(A) to W_(Void) ratio can be 4,6, 8, 10, or 12. Additionally, or alternatively, this low-spin driverface surface texture may be characterized by a W_(VDCL) value, measuredin a Y-Z plane through the face center, that is greater than about 18%,or greater than about 20%, or greater than about 22%, or greater thanabout 24%, or greater than about 26%, or greater than about 28%, orgreater than about 30%. In some embodiments, the W_(VDCL) value canrange from 18% to 33%, 18% to 24%, 24% to 36%, 24% to 30%, 30% to 36%,or 27% to 33%. For example, the W_(VDCL) value can be 18%, 20%, 22%,24%, 26%, 28%, 30%, 32%, 34%, or 36%.

In a second embodiment, a metal wood intended to induce a greater amountof loft (i.e., having a loft angle of from about 12 degrees to about 28degrees, or from about 14 degrees to about 24 degrees) may bespecifically designed to have a higher backspin tendency by including amilled strike face with a surface texture characterized by an R_(A) toW_(Void) ratio, measured in a Y-Z plane through the face center, that isless than about 4, or less than about 3, or less than about 2, or withina range of from about 1 to about 4, or from about 2 to about 4.Additionally, or alternatively, this higher-spin face surface texturemay be characterized by a W_(VDCL) value, measured in a Y-Z planethrough the face center, that is less than about 24%, or less than about22%, or less than about 20%, or less than about 18%, or within a rangeof from about 20% to about 24%.

In either of these embodiments, instead of simply being a singlereading, the R_(A) to W_(Void) and W_(VDCL) values may be an average ofthe values across a plurality of Y-Z slices. For example, these valuesmay be averaged across a center strip, region, or portion of the face12. For example, these values may be averaged across a 1.68 inch (42.67mm) impact zone, measured along the X-axis, and centered about facecenter. Likewise, in some variations, these low or high backspin surfacetextures may be localized within a center portion 252 of the face, suchas within a 1.68 inch diameter circle centered about the face center.Alternatively, these values may be averaged across a narrower centerportion of the impact zone that may measure about 0.375 inches (about9.53 mm) along the X-axis or in diameter.

In an embodiment, in an effort to maximize contact friction in aheel-toe direction, a strike face 12 may include a milled surfacetexture characterized by an R_(A) to W_(Void) ratio, measured in an X-Zplane through the face center, that is greater than about 4, or greaterthan about 5, or greater than about 6, or greater than about 7, orgreater than about 8, greater than about 9, or greater than about 10.Additionally, or alternatively, this surface texture with directionallyincreased contract friction may be characterized by a W_(VDCL) value,measured in an X-Z plane through the face center, that is greater thanabout 24%, or greater than about 26%, or greater than about 28%, orgreater than about 30%. In some embodiments, the W_(VDCL) value canrange from 24% to 36%, 24% to 30%, 30% to 36%, or 27% to 33%. Forexample, the W_(VDCL) value can be 24%, 26%, 28%, 30%, 32%, 34%, or 36%.

Alternatively, to minimize the contact friction in a heel-toe directiona strike face 12 may include a milled surface texture characterized byan R_(A) to W_(Void) ratio, measured in an X-Z plane through the facecenter, that is less than about 4, or less than about 3, or less thanabout 2, or within a range of from about 1 to about 4, or from about 2to about 4. Additionally, or alternatively, this surface texture withdirectionally decreased contract friction may be characterized by aW_(VDCL) value, measured in an X-Z plane through the face center, thatis less than about 24%, or less than about 22%, or less than about 20%,or less than about 18%, or within a range of from about 20% to about24%.

While the above-described embodiments discuss increasing contactfriction (which decreases backspin in a driver) in/around the center ofthe strike face 12, in other embodiments, contact friction may bepromoted or discouraged in other locations or areas about the strikeface 12 via changes in the surface texture. For example, the surfacetexture in a peripheral region (or peripheral portion 254) of the strikeface 12 (e.g., outside of the central region or narrower, center portion252) may be controlled to provide enhanced forgiveness, alter spinprofiles, and/or to offset other design parameters of the club head 10.

In one embodiment, contact friction may be increased in the peripheralregion by providing an R_(A) to W_(Void) ratio, measured in the Y-Zplane and/or in the X-Z plane and averaged across at least a portion ofthe peripheral region, of greater than about 4, or greater than about 5,or greater than about 6, or greater than about 7, or greater than about8, greater than about 9, or greater than about 10. Additionally, oralternatively, this increased friction peripheral region may have asurface texture characterized by a W_(VDCL) value, measured in the Y-Zplane and/or in the X-Z plane and averaged across at least a portion ofthe peripheral region, that is greater than about 18%, or greater thanabout 20%, or greater than about 22%, or greater than about 24%, orgreater than about 26%, or greater than about 28%, or greater than about30%. In some embodiments, the W_(VDCL) value can range from 18% to 33%,18% to 24%, 24% to 36%, 24% to 30%, 30% to 36%, or 27% to 33%. Forexample, the W_(VDCL) value can be 18%, 20%, 22%, 24%, 26%, 28%, 30%,32%, 34%, or 36%. The increased friction peripheral region mayspecifically include one or more of an increased friction portionabutting the sole 28, an increased friction portion abutting the toeportion 20, an increased friction portion abutting the crown 26, and/oran increased friction portion abutting the heel portion 22.

In some embodiments, the increased contact friction in the peripheralregion may be used to, for example, provide additional designflexibility in altering the bulge and/or roll radius of curvature of thestrike face 12 or the center of gravity of the club head 10, or inincreasing the forgiveness to certain impacts.

In an embodiment, contact friction may be decreased in the peripheralregion by providing an R_(A) to W_(Void) ratio, measured in the Y-Zplane and/or in the X-Z plane and averaged across at least a portion ofthe peripheral region, of less than about 4, or less than about 3, orless than about 2, or within a range of from about 1 to about 4, or fromabout 2 to about 4. Additionally, or alternatively, this decreasedfriction peripheral region may have a surface texture characterized by aW_(VDCL) value, measured in the Y-Z plane and/or in the X-Z plane andaveraged across at least a portion of the peripheral region, that isless than about 24%, or less than about 22%, or less than about 20%, orless than about 18%, or within a range of from about 20% to about 24%.The decreased friction peripheral region may specifically include one ormore of a decreased friction portion abutting the sole 28, a decreasedfriction portion abutting the toe portion 20, a decreased frictionportion abutting the crown 26, and/or a decreased friction portionabutting the heel portion 22.

In some embodiments, an average R_(A) to W_(Void) ratio and/or W_(VDCL)value from within the central region or narrower, center portion 252 ofthe strike face 12 may be different than the average R_(A) to W_(Void)ratio and/or W_(VDCL) value from within a portion of the peripheralregion of the strike face 12. In another embodiment, the R_(A) toW_(Void) ratio and/or W_(VDCL) value may vary as a function of anincreasing distance from the geometric center of the strike face 12. Inan embodiment, an average R_(A) to W_(Void) ratio and/or W_(VDCL) value(measured in one or both of the Y-Z plane and the X-Z plane) may begreater proximate the toe portion 20 and/or heel portion 22 than in thecenter of the strike face 12.

In practice, the R_(A) to W_(Void) ratio and W_(VDCL) value for aparticular face may be customized during a milling process by alteringone or more of the tool (e.g., a ball end mill, a square end mill, or acorner round end mill), the angle of the tool relative to the face(e.g., from greater than about 0 degrees relative to the face to about90 degrees), the cutting speed (e.g., from about 60 to about 300 inchesper minute for titanium, or from about 300 to about 1000 inches perminute for steel), the stepover (e.g., from about 0.005 inch to about0.125 inch), and the travel velocity (e.g., from about 0.005 to about0.010 inch/minute).

Understanding that both the R_(A) to W_(Void) ratio and W_(VDCL)correlate well with the spin that may be imparted to an impacted golfball, it may also be desirable to provide a coordinated set of golfclubs that vary the R_(A) to W_(Void) ratio and W_(VDCL) (taken withinthe Y-Z plane through face center) as a function of the loft angle ofthe club head. For example, in a low lofted club, spin may be lessdesirable than in a comparatively higher lofted club. As such, themilling pattern/surface texture provided on the face may be specificallycontrolled to support the design objectives of the club head.

In one embodiment, a set of golf clubs may comprise three golf clubs,each having a different loft angle (L), where L₁<L₂<L₃. In this set,each golf club may have a progressively decreasing R_(A)/W_(Void) ratio(i.e., where (R_(A)/W_(Void))₁>(R_(A)/W_(Void))₂>(R_(A)/W_(Void))₃),and/or a progressively decreasing W_(VDCL) value (i.e., whereW_(VDCL1)>W_(VDCL2)>W_(VDCL3)). In one embodiment, at least the first ofthe three clubs (indicated with a subscript “1” in the relationshipsabove) is a wood-style club, and may be a driver having a loft of fromabout 8 degrees to about 12 degrees. In an embodiment, at least thethird golf club of the set (indicated with a subscript “3” in therelationships above) may be an iron-type golf club. In an embodiment, L₃may be less than or equal to about 24 degrees. Finally, in anembodiment, all three clubs in the set may be wood-style golf clubs orall three may be iron-style golf clubs.

It should further be noted that the inverse correlation between spin andboth R_(A) to W_(Void) ratio and W_(VDCL) generally only applies forlower lofted club heads (i.e., loft angles of from about 8 to about 24degrees). For higher lofted club heads (i.e., loft angles greater thanabout 30 degrees), the opposite effect may exist. More specifically, inhigher lofted club heads, spin may increase with a correspondingincrease in both R_(A) to W_(Void) ratio and W_(VDCL). It is believedthat this transition occurs due to the change in the magnitude of theshear impact forces as the loft and impact angle increases (i.e., wherea driver imparts predominantly a compressive force to a golf ball, awedge imparts a much more substantial shear force).

Therefore, in an embodiment, a high-lofted iron (i.e., having a loftangle of from about 30 to about 64 degrees, or from about 34 to about 64degrees, or from about 39 to about 64 degrees), may be specificallydesigned to have a high backspin tendency by including a milled strikeface with surface texture characterized by an R_(A) to W_(Void) ratio,measured in a Y-Z plane through the face center, that is greater thanabout 4, or greater than about 5, or greater than about 6, or greaterthan about 7, or greater than about 8, greater than about 9, or greaterthan about 10. In some embodiments, the R_(A) to W_(Void) ratio canrange from 4 to 12, 4 to 8, 8 to 12, 6 to 10, 4 to 6, 36 to 8, 8 to 10,or 10 to 12. For example, the R_(A) to W_(Void) ratio can be 4, 6, 8,10, or 12. Additionally, or alternatively, this high-spin iron facesurface texture may be characterized by a W_(VDCL) value, measured in aY-Z plane through the face center, that is greater than about 18%, orgreater than about 20%, or greater than about 22%, or greater than about24%, or greater than about 26%, or greater than about 28%, or greaterthan about 30%. In some embodiments, the W_(VDCL) value can range from18% to 33%, 18% to 24%, 24% to 36%, 24% to 30%, 30% to 36%, or 27% to33%. For example, the W_(VDCL) value can be 18%, 20%, 22%, 24%, 26%,28%, 30%, 32%, 34%, or 36%.

Likewise, in an embodiment, a set of golf clubs may comprise three golfclubs, each having a different loft angle (L), where L₁<L₂<L₃. In thisset, each golf club may have an R_(A)/W_(Void) ratio where(R_(A)/W_(Void))₁>(R_(A)/W_(Void))₂ and(R_(A)/W_(Void))₃>(R_(A)/W_(Void))₂. Alternatively, or in addition, eachclub may have a W_(VDCL) value where W_(VDCL1)>W_(VDCL2) andW_(VDCL3)>W_(VDCL2). In an embodiment, at least the first of the threeclubs (indicated with a subscript “1” in the relationships above) is awood-style club, and may be a driver having a loft of from about 8degrees to about 12 degrees, and the third of the three clubs (indicatedwith a subscript “3” in the relationships above) is an iron-type clubhaving a loft of from about 30 to about 64 degrees, or from about 34 toabout 64 degrees, or from about 39 to about 64 degrees.

Replacement of one or more claimed elements constitutes reconstructionand not repair. Additionally, benefits, other advantages, and solutionsto problems have been described with regard to specific embodiments. Thebenefits, advantages, solutions to problems, and any element or elementsthat may cause any benefit, advantage, or solution to occur or becomemore pronounced, however, are not to be construed as critical, required,or essential features or elements of any or all of the claims, unlesssuch benefits, advantages, solutions, or elements are expressly statedin such claims.

As the rules to golf may change from time to time (e.g., new regulationsmay be adopted or old rules may be eliminated or modified by golfstandard organizations and/or governing bodies such as the United StatesGolf Association (USGA), the Royal and Ancient Golf Club of St. Andrews(R&A), etc.), golf equipment related to the apparatus, methods, andarticles of manufacture described herein may be conforming ornon-conforming to the rules of golf at any particular time. Accordingly,golf equipment related to the apparatus, methods, and articles ofmanufacture described herein may be advertised, offered for sale, and/orsold as conforming or non-conforming golf equipment. The apparatus,methods, and articles of manufacture described herein are not limited inthis regard.

While the above examples may be described in connection with aniron-type golf club, the apparatus, methods, and articles of manufacturedescribed herein may be applicable to other types of golf club such as adriver wood-type golf club, a fairway wood-type golf club, a hybrid-typegolf club, an iron-type golf club, a wedge-type golf club, or aputter-type golf club. Alternatively, the apparatus, methods, andarticles of manufacture described herein may be applicable to othertypes of sports equipment such as a hockey stick, a tennis racket, afishing pole, a ski pole, etc.

Moreover, embodiments and limitations disclosed herein are not dedicatedto the public under the doctrine of dedication if the embodiments and/orlimitations: (1) are not expressly claimed in the claims; and (2) are orare potentially equivalents of express elements and/or limitations inthe claims under the doctrine of equivalents.

Various features and advantages and features of the disclosure arefurther set forth in the following clauses:

The invention claimed is:
 1. A wood-style golf club head comprising: astrike face and a body that cooperate to define a hollow internal clubhead volume, the strike face further comprising a ball striking surfacehaving a surface texture characteristic of milling; the surface textureis uniform across the entire strike face when measured in any onedirection and comprises a plurality of peaks, a plurality of valleys,and a reference mid-plane extending in between the plurality of peaksand the plurality of valleys, wherein below the reference mid-plane is anegative distance, and above the reference mid-plane is a positivedistance, and the plurality of peaks and the plurality of valleys extendan average maximum distance of at least −140 micro inches (−3.56 micrometers) to at least 140 micro inches (−3.56 micro meters); the surfacetexture further comprises a central portion that is surrounded by aperipheral portion; the central portion is round and comprises a firstconcentric milling pattern extending outward from a center of thecentral portion; the peripheral portion comprises a second millingpattern different from the first concentric milling pattern; the surfacetexture further comprises an average surface roughness (RA),representing an arithmetic average value of absolute surface deviationsrelative to a mean center line, a surface void parameter (WVoid),representing an average depth of the plurality of valleys relative to aclosed reference surface created using a morphologic closing filterapplied to the surface texture, and a surface contact parameter (WVDCL),representing the amount of contact between the closed reference surfaceand the surface texture; and wherein the surface texture, measuredwithin at least one of a vertical cutting plane or a second cuttingplane that is orthogonal to both the vertical cutting plane and the ballstriking surface, is characterized by at least one of: a ratio of RA toWVoid being greater than about 4; or, a WVDCL parameter being greaterthan about 24%.
 2. The golf club head of claim 1, wherein the ballstriking surface further comprises a cup face, such that a strike plateand a frame are integrally formed with each other; and wherein the cupface extends rearward to form a portion of a crown and a sole.
 3. Thegolf club head of claim 2, wherein the ball striking surface furthercomprises a back surface; wherein the back surface is milled andmachined to adjust at least one of: a thickness of the ball strikingsurface, a bulge radius of the ball striking surface, or a roll radiusof the ball striking surface.
 4. The golf club head of claim 3, whereinthe back surface comprises a back surface texture that varies as afunction of a distance from a geometric center of the strike face. 5.The golf club head of claim 1, wherein the RA is measured using ahigh-pass filter having a 0.762 mm cutoff, the WVoid parameter ismeasured using a 0.127 mm radius closing filter, and the WVDCL parameteris measured using a 0.508 mm radius closing filter.
 6. The golf clubhead of claim 1, wherein the surface texture is further characterized byat least one of: the ratio of RA to WVoid being greater than about 8;or, the WVDCL parameter being greater than about 28%.
 7. The golf clubhead of claim 1, wherein the plurality of peaks comprises a plurality ofsmaller valleys; and wherein the plurality of valleys comprises aplurality of smaller peaks.
 8. The golf club head of claim 1, whereinthe surface texture varies as a function of a distance from a geometriccenter of the strike face.
 9. The golf club head of claim 1, wherein thesurface texture is further characterized by at least one of the ratiosof RA to WVoid or the WVDCL parameter being greater within theperipheral portion than within the central portion.
 10. A wood-stylegolf club head comprising: a strike face and a body that cooperate todefine a hollow internal club head volume, the strike face furthercomprising a ball striking surface having a surface texturecharacteristic of milling; wherein the strike face is disposed at a loftangle of from 8 degrees to 24 degrees; the surface texture is uniformacross the entire strike face when measured in any one direction andcomprises a plurality of peaks, a plurality of valleys, and a referencemid-plane extending in between the plurality of peaks and the pluralityof valleys, wherein below the reference mid-plane is a negativedistance, and above the reference mid-plane is a positive distance, andthe plurality of peaks and the plurality of valleys extend an averagemaximum distance of at least −200 micro inches (−5.08 micro meters) toat least 200 micro inches (5.08 micro meters); the surface texturefurther comprises a central portion that is surrounded by a peripheralportion; the central portion is round and comprises at least a firstmilling pattern extending outward from a center of the central portion;a peripheral portion comprising at least a second milling patterndifferent from the first milling pattern; the surface texture furthercomprises an average surface roughness (RA), representing an arithmeticaverage value of absolute surface deviations relative to a mean centerline, a surface void parameter (WVoid), representing an average depth ofthe plurality of valleys relative to a closed reference surface createdusing a morphologic closing filter applied to the surface texture, and asurface contact parameter (WVDCL), representing the amount of contactbetween the closed reference surface and the surface texture; andwherein the surface texture, measured within at least one of a verticalcutting plane or a second cutting plane that is orthogonal to both thevertical cutting plane and the ball striking surface, is characterizedby at least one of: a ratio of RA to WVoid being greater than about 4;or, a WVDCL parameter being greater than about 24%.
 11. The golf clubhead of claim 10, wherein the surface texture, measured within avertical cutting plane offset from a geometric center of the strikeface, is characterized by the ratio of RA to WVoid being greater thanthe ratio of RA to WVoid measured within the plane that intersects thegeometric center; or, the WVDCL parameter being greater than the WVDCLparameter measured within the plane that intersects the geometriccenter.
 12. The golf club head of claim 10, wherein the surface texture,measured within the vertical cutting plane extending through a geometriccenter of the strike face, is further characterized by an RA of betweenabout 140 μ-in and about 300 μ-in.
 13. The golf club head of claim 10,wherein the ball striking surface comprises a back surface; wherein theback surface is milled and machined to adjust at least one of: athickness of the ball striking surface, a bulge radius of the ballstriking surface, or a roll radius of the ball striking surface.
 14. Thegolf club head of claim 10, wherein the ball striking surface comprisesa first region having a first surface texture and a second region havinga second surface texture; and wherein at least one of: an average ratioof RA to WVoid measured within a vertical cutting plane is differentbetween the first region and the second region; or, an average WVDCLparameter measured within a vertical cutting plane is different betweenthe first region and the second region.
 15. The golf club head of claim10, wherein a strike plate and a frame are integrally formed such thatthe strike plate and frame cooperate to define the ball strikingsurface; and wherein the cup face extends rearward to form a portion ofa crown and a sole.
 16. The golf club head of claim 15, wherein the ballstriking surface comprises a back surface; wherein the back surface ismilled and machined to adjust at least one of: a thickness of the ballstriking surface, a bulge radius of the ball striking surface, or a rollradius of the ball striking surface.
 17. The golf club head of claim 16,wherein the back surface comprises a back surface texture that varies asa function of a distance from a geometric center of the strike face. 18.The golf club head of claim 10, wherein the surface texture is furthercharacterized by at least one of: a ratio of RA to WVoid being greaterthan about 8; or, the WVDCL parameter being greater than about 28%. 19.The golf club head of claim 10, further comprising a body that extendsrearward from the ball striking surface, wherein the body and the strikeface form a hollow interior volume.
 20. The golf club head of claim 10,wherein the strike face includes: a strike plate having an outerperimeter; and a frame surrounding the strike plate, wherein the strikeplate is welded to the frame across the entire outer perimeter; andwherein the ball striking surface and the surface texture extendcontinuously across both the strike plate and the frame.